Department of Atmospheric and Oceanic Sciences and Laboratory for Climate and Ocean-Atmosphere Studies, School of Physics, Peking University, Beijing 100871, China.
Environ Sci Technol. 2023 Jun 13;57(23):8701-8707. doi: 10.1021/acs.est.3c01517. Epub 2023 Jun 2.
Acidity is one of the most fundamental properties of atmospheric aerosol particles, influencing both chemical processes and environmental impacts. A couple of methods for measuring the pH of aerosol particles have been developed, yet no approach is currently available for quantifying the pH of suspending submicron particles. We developed an aerosol fluorescence cell (AFC) for quantifying the pH of aerosol particles in a continuous flow. Particles containing fluorescent pH probes (fluorescein and Oregon green 488) were injected into the AFC. Ratiometric analysis of pH for these particles was conducted by alternatively exciting them with two wavelengths of diode lasers (450 and 488 nm). The employment of the two types of fluorescent probes allowed the measurement of pH in the range of 2-7. The pH measurement by the AFC for submicron particles was compared with that measured by using pH indicator papers, providing a reasonably good agreement. Measurement of size-selected particles suggested that the AFC approach is applicable to particles of 80 nm in diameter. In combination with recent developments for analyzing renebulized water-soluble matter samples, we suggest that the AFC method can be applied not only for laboratory standards but also for atmospherically relevant samples in the future.
酸度是大气气溶胶粒子的最基本性质之一，影响着化学过程和环境影响。已经开发出了几种测量气溶胶粒子 pH 值的方法，但目前还没有一种方法可以定量测量悬浮亚微米粒子的 pH 值。我们开发了一种气溶胶荧光细胞 (AFC)，用于在连续流中定量测量气溶胶粒子的 pH 值。将含有荧光 pH 探针（荧光素和 Oregon green 488）的粒子注入 AFC。通过交替用两种二极管激光器（450nm 和 488nm）激发这些粒子来进行 pH 值的比率分析。这两种荧光探针的使用使得可以测量 2-7 的 pH 值范围。AFC 对亚微米粒子的 pH 值测量与使用 pH 指示剂纸测量的结果进行了比较，结果相当吻合。对粒径选择的粒子的测量表明，AFC 方法适用于直径为 80nm 的粒子。结合最近开发的分析再润湿性水溶性物质样品的方法，我们建议 AFC 方法不仅可以用于实验室标准，而且将来也可以用于与大气相关的样品。
